Resolve the incorrect use of srcdir and builddir references for
various files in the build system. These have crept in over time
and went unnoticed because when building in the top level directory
srcdir and builddir are identical.
With this change it's again possible to build in a subdirectory.
$ mkdir obj
$ cd obj
$ ../configure
$ make
Reviewed-by: loli10K <ezomori.nozomu@gmail.com>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Don Brady <don.brady@delphix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#8921Closes#8943
